1. Field of the Invention
The present invention relates to an intake manifold for an engine, in particular to a mounting position of a negative pressure check valve provided for an intake manifold.
2. Description of the Related Art
Conventionally, an air actuator using negative pressure in a vacuum chamber is widely employed in various applications. Negative pressure is induced inside a surge tank of an intake manifold and fluctuates, and the lowest negative pressure is maintained in the vacuum chamber. The air actuator is arranged nearby the intake manifold, and is used to carry out open/shut operations of an intake valve that generates air column resonance, in immediate response to the engine operations. The negative pressure is accumulated and maintained inside the vacuum chamber by using a negative pressure check valve, which opens only when the pressure inside the surge tank becomes lower than the pressure inside the vacuum chamber. Therefore the vacuum chamber stores the negative pressure induced by the air pulsation or air dynamics inside the surge tank (i.e., creates a stronger vacuum). Japanese unexamined patent publication (KOKAI) No. 8-100722 discloses an intake manifold that arranges the vacuum chamber next to the surge tank and provides the negative pressure check valve on a partition wall between the vacuum chamber and the surge tank, so as to make the structure relating to the vacuum chamber and the negative pressure check valve compact.